Biometric sensing devices are increasingly common in computer or network security applications, financial applications, and surveillance applications. Biometric sensing devices detect or image a unique physical or behavioral trait of a person, providing biometric data that can reliably identify the person. For example, a fingerprint includes a unique pattern of ridges and valleys that can be imaged by a fingerprint sensing device. The image of the fingerprint, or the unique characteristics of the fingerprint, can be compared to reference data, such as a reference fingerprint image. The identity of the person is obtained or verified when the newly captured fingerprint image matches the reference fingerprint image.
A cover glass or substrate may be positioned above a biometric sensing device to act as an input surface for the biometric sensing device, or to protect the biometric sensing device from damage and environmental conditions. In some instances, the substrate material or the thickness of the substrate can adversely impact the performance of the biometric sensing device. For example, an image captured by a biometric sensing device may be blurry due to the sensed fields dispersing or spreading out as the sensed fields pass through the substrate. It can be difficult to resolve details or features in the image because the thickness of the substrate limits the resolution of a captured image.